In recent years, with the development of science and technology, various display devices are gradually developed. On this basis, the requirements on the performance of display device are also getting higher and higher. Based on this, for the backlight of the display device, a vertical collimated light beam is desired.
However, in a backlight module, light from the light source is emitted in all directions. Therefore, even if the backlight module is modulated, it is difficult for the backlight module to emit a collimated light beam.